/*
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You under the Apache License, Version 2.0
 * (the "License"); you may not use this file except in compliance with
 * the License.  You may obtain a copy of the License at
 * 
 *      http://www.apache.org/licenses/LICENSE-2.0
 * 
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package org.apache.tomcat.util.modeler;

import javax.management.AttributeChangeNotification;
import javax.management.Notification;
import javax.management.NotificationFilter;
import java.util.HashSet;

/**
 * <p>Implementation of <code>NotificationFilter</code> for attribute change
 * notifications.  This class is used by <code>BaseModelMBean</code> to
 * construct attribute change notification event filters when a filter is not
 * supplied by the application.</p>
 *
 * @author Craig R. McClanahan
 */
public class BaseAttributeFilter implements NotificationFilter {

	private static final long serialVersionUID = 1L;

	// ----------------------------------------------------------- Constructors
	/**
	 * The set of attribute names that are accepted by this filter.  If this
	 * list is empty, all attribute names are accepted.
	 */
	private HashSet<String> names = new HashSet<String>();


	// ----------------------------------------------------- Instance Variables

	/**
	 * Construct a new filter that accepts only the specified attribute
	 * name.
	 *
	 * @param name Name of the attribute to be accepted by this filter, or
	 *             <code>null</code> to accept all attribute names
	 */
	public BaseAttributeFilter(String name) {

		super();
		if (name != null)
			addAttribute(name);

	}


	// --------------------------------------------------------- Public Methods

	/**
	 * Add a new attribute name to the set of names accepted by this filter.
	 *
	 * @param name Name of the attribute to be accepted
	 */
	public void addAttribute(String name) {

		synchronized (names) {
			names.add(name);
		}

	}

	/**
	 * Clear all accepted names from this filter, so that it will accept
	 * all attribute names.
	 */
	public void clear() {

		synchronized (names) {
			names.clear();
		}

	}

	/**
	 * Return the set of names that are accepted by this filter.  If this
	 * filter accepts all attribute names, a zero length array will be
	 * returned.
	 */
	public String[] getNames() {

		synchronized (names) {
			return names.toArray(new String[names.size()]);
		}

	}

	/**
	 * <p>Test whether notification enabled for this event.
	 * Return true if:</p>
	 * <ul>
	 * <li>This is an attribute change notification</li>
	 * <li>Either the set of accepted names is empty (implying that all
	 * attribute names are of interest) or the set of accepted names
	 * includes the name of the attribute in this notification</li>
	 * </ul>
	 */
	@Override
	public boolean isNotificationEnabled(Notification notification) {

		if (notification == null)
			return (false);
		if (!(notification instanceof AttributeChangeNotification))
			return (false);
		AttributeChangeNotification acn =
				(AttributeChangeNotification) notification;
		if (!AttributeChangeNotification.ATTRIBUTE_CHANGE.equals(acn.getType()))
			return (false);
		synchronized (names) {
			if (names.size() < 1)
				return (true);
			else
				return (names.contains(acn.getAttributeName()));
		}

	}

	/**
	 * Remove an attribute name from the set of names accepted by this
	 * filter.
	 *
	 * @param name Name of the attribute to be removed
	 */
	public void removeAttribute(String name) {

		synchronized (names) {
			names.remove(name);
		}

	}


}
